Fixes

[alexdalitz]

Timeout::Error, untainted, and Ruby > 2.7.0

[alexdalitz]

@keithrbennett Could you please review this PR for me?

[keithrbennett]

Review finished. Thanks!

[alexdalitz]

Thanks @keithrbennett!
Once you're happy with this and approve it, I'll merge it in.
I'm hoping to release a dnsruby-1.73.0 later this week with all these changes in it.

[keithrbennett]

Hi, Alex. I just realized that the version of Ruby that ships with macOS is 2.6! So if anyone is actually using that old a version using the system Ruby, then they will be unable to use dnsruby without changing their setup (using rvm or another version manager). Do we care? It's highly unlikely that anyone with any kind of important application is still using such an old version.

[keithrbennett]

If we stay with the Ruby version >= 2.8 requirement, the code changes look good to me.

[alexdalitz]

Thanks @keithrbennett !

I've moved the Ruby requirement from 2.7 to 2.8 - if you're worried about 2.6, then it's been a long time since we supported that...